Silica Gel Adsorption Research Articles

Experimental comparison of solar‐powered adsorption‐based atmospheric water harvesting using air‐to‐air & water‐to‐air heat exchanger for condensation

AbstractAdsorption‐focused technologies for atmospheric water harvesting is of great importance. Most of the available systems in the literature use glass as a condenser, which gets heated up. This restricts vapor condensation to harvest less water and hampers the system's scalability. The effectiveness of the proposed solar atmospheric water harvesting system, which uses an air‐to‐air fin‐tube heat exchanger to condense the vapors, is experimentally evaluated in this work. In order to assess the system's effectiveness using a water‐to‐air fin‐tube heat exchanger, a comparison study is also carried out. The experimental setup consists of evacuated tube solar air heater having 8.46 m2 area and 15 kg silica gel adsorbent. The performance metrics for comparison include adsorption & regeneration rate, thermal, overall and exergy efficiency, along with economic analyses. The system harvests 1890 mL/day of water using air‐to‐air heat exchanger at cost of 0.19 $/l, achieving thermal, overall & exergy efficiencies of 21.66%, 2.24%, and 6.51%, respectively. On the other hand, the water‐to‐air heat exchanger based system harvests maximum of 2680 mL/day of water at a cost of 0.14 $/l, achieving thermal, overall & exergy efficiencies of 25.65%, 3.34%, and 9.13%, respectively. Moreover, the produced water is confirmed to be safe for consumption.

Optimization of Cadmium Removal Using Tetraethylene Glycol-Modified Silica-Based Adsorbent via Response Surface Methodology

In solid-phase extraction for preconcentration, silica (Si) is the most commonly used as an adsorbent. However, the selectivity and effectiveness of silica gel adsorption on metal ions are low, so it needs to be modified to improve the adsorption capability. The modification was done using reflux and oven heating in the modification silica with 3-glycidoxypropyl trimethoxysilane (GPTMS) and tetraethylene glycol (TEG). A central composite design batch process determined the optimum conditions for cadmium adsorption. TEG-modified silica was successfully synthesized and characterized using FTIR spectroscopy, SEM, and elemental analyzers. Peaks of C-H and epoxy on FTIR spectra showed that Si- GPTMS was formed. The increase of %C and %H from the first to the second step indicated that Si-TEG was successfully synthesized. There was no significant difference in silica particle morphology on SEM before and after modification. The reflux method gave a higher yield compared to the heating method. The constant stirring by the magnetic bar and solvent cycle in the reflux method catalyzed the reaction. This study found that at pH 7, 30 mg of adsorbent weight at 35°C and 22 minutes of contact time were optimum Cd2+ adsorption conditions. As the weight of the adsorbent increases, the adsorption capacity decreases. Contact time and temperature have no significant effect on Cd adsorption by Si-TEG.

Optimasi Adsorpsi Ion Fe3+ Menggunakan Adsorben Silika Gel Sulfonat

Adsorption is a process of absorption of adsorbate or substances absorbed by the surface of the adsorbent or absorbent substance which aims to reduce the Fe3+ cation in a solution. Research has been carried out on the adsorption of Fe3+ cations using silica sulfonate adsorbents by varying the pH and contact time to obtain optimum conditions during adsorptions. The adsorption process of Fe3+ cations used a sulfonate modified silica gel adsorbent has been carried out by varying the pH, namely 2; 3; 4; 5; 6; 7 and the maximum pH has been fixed at pH 6 with an abdorption capacity of 2,32732 mg/g with an absorpyion percentage of 78.79 %, contact time variations of 15; 30; 45; 60; 75 minutes have been obtained for optimum contact time at 45 minutes with an absorption capacity of 2,225756 mg/g and absorption percent of 77,33 %

Catalytic activity of modified silica gel adsorbents under conditions of methanol conversion from water-methanol waste of natural gas

The work is devoted to the analysis of factors affecting the catalytic activity of modified silica gel adsorbents under conditions of methanol conversion to dimethyl ether. The objects of the study were the initial and modified silica gel adsorbents ASM, ASM VS, BASF KC-Trockenperlen H and BASF KC-Trockenperlen WS used in the purification of methanol from water‒methanol waste of natural gas. The purpose of this paper is to study the effect of the specific surface area, elemental and phase composition, and operating time of adsorbents on the catalytic activity of modified silica gel adsorbents under conditions of methanol conversion to dimethyl ether. The composition and structural characteristics of the samples were determined by X‒ray fluorescence, X-ray diffraction analysis and low-temperature nitrogen adsorption. Based on the results of IR‒spectrometric and thermal studies, changes in the structure of the surfaces of adsorbents during their operation by various components of organic origin were evaluated. The catalytic activity of silica gel adsorbents in methanol conversion was studied in a fixed bed reactor at atmospheric pressure in the range of 120-290°C and an optimized rate of methanol-saturated nitrogen flow of 1200 ml/min. The methanol conversion process was controlled by gas‒liquid chromatography. An increase of the catalytic activity of adsorbents in methanol conversion to dimethyl ether was found in the range of ASM VS < BASF KC-Trockenperlen WS < BASF KC-Trockenperlen H < ASM. The maximum catalytic activity at 290°C was shown by the adsorbent ASM with 4.2% aluminum oxide and an amorphous structure, which significantly reduces methanol emissions into the atmosphere. For crystalline adsorbents ASM VS with an alumina content of 13.2%, the catalytic activity was minimal. It is shown that the decrease in the catalytic activity of adsorbents in gas treatment unit during operation is associated with a decrease in the value of the specific surface area of samples with a constant content of aluminum oxide and phase state, which is associated with the possible blocking of the catalytic centers of adsorbents due to the accumulation of components of organic origin in the process of natural gas purification. The establishment of factors affecting the methanol conversion to dimethyl ether on modified silica gel adsorbents will allow managing environmental risks, as well as reducing risks to humans during transportation and disposal of water-methanol waste from natural gas purification.

Adsorption of Cu(II) on silica gel synthesized from chemical bottle glass waste: Response surface methodology-Box Behnken design optimization

Recent research has reported on the extraction and synthesis of silica gels from a waste glass of chemicals. This study aims to optimize silica gel synthesized from chemical glass waste as heavy metal adsorbent Cu2+. Silica gel adsorbent has been successfully synthesized by reacting silica from chemical glass waste and sodium hydroxide (NaOH) by a fusion reaction and sol–gel process. Synthesized silica gel has an amorphous diffractogram at 2θ 20–30°, a purity of 75.63 %, a surface area of 297.08 m2/g, and a pore radius of 15.74 nm. The adsorption formulation was optimized using Design Box–Behnken and optimum conditions were obtained at adsorbent doses close to 3.5 g, initial concentration 50–100 ppm, contact time 10 min, and pH 9. Adsorption Isotherm Langmuir, Freundlich, Temkin, and Dubinin–Raduskevich were investigated to determine the mechanism of adsorption. Adsorption data show that the adsorption is well-fitted to the Langmuir isotherm model. The results of SEM–EDX characterization showed that the surface morphology of silica gel showed a spherical and irregular surface then after adsorption cu metal was distributed on the surface of the silica gel. Based on all the results of the study it can be indicated that silica gel synthesized from chemical glass bottle waste can be applied as adsorbent Cu2+.

Green synthesis of silica gel adsorbents: microwave boosts silanol groups for improved moisture uptake

This research investigates the influence of microwave irradiation on the silanol content and moisture adsorption capacity of silica gel prepared from clear glass waste. Employing a green and efficient microwave-assisted synthesis method, we demonstrate rapid formation of silica gel with enhanced properties. Fourier-transform infrared (FTIR) analysis confirms the presence of silanol (Si-OH) groups on the synthesized gel, with a focus on the characteristic peak at 956.44 cm⁻¹ indicating their abundance. Notably, the peak area of this peak significantly increases with increasing irradiation time (5 to 15 minutes). This translates to a parallel increase in moisture adsorption capacity, rising from 56% to 82%. The enhanced silanol content suggests the potential of microwave-derived silica gel as a high-performance desiccant, as these groups directly contribute to moisture binding. Our findings highlight the promising potential of waste glass valorization via microwave synthesis for developing sustainable and effective moisture adsorbents.

Preparation and assessment of ionic liquid and few-layered graphene composites to enhance heat and mass transfer in adsorption cooling and desalination systems

Adsorption systems can utilise low-temperature renewable and waste heat sources, which have emerged as a feasible alternative to conventional water desalination and cooling systems. However, the material of poor heat and mass transfer performance stall their widespread utilisation. This article presents the development and investigation of new composites employing few-layered graphene platelets and ionic liquids, namely ethyl-methylimidazolium methane sulfonate ([EMIM][CH3SO3]) and Ethyl-methylimidazolium-chloride ([EMIM][Cl]) to address such challenges. The impact of the few-layered graphene platelets, thermal properties, water adsorption properties of the developed composites and their thermal diffusivity were experimentally investigated. Besides, the overall cyclic performance was studied experimentally at the material level and computationally at the component level by employing a previously validated 2D dynamic heat and mass transfer model. The experimental investigation indicated that pristine few-layered graphene has a surface area of 56.8978 m2/g and a relatively high thermal diffusivity of 22.23 mm2/s. The developed composites showed higher thermal diffusivity than the baseline adsorbent silica gel. The highest thermal diffusivity was 11.84 mm2/s for GP-CH3SO3-10, 394 times higher than silica gel. Water adsorption characteristics of the composites were carried out, and the Dubinin–Astakhov (D-A) model was employed to model the experimental isotherms with good accuracy. The cumulative advanced adsorption and thermal characteristics of the developed composites resulted in higher cyclic performance by up to 82 % and 85 % than that of the baseline silica gel.

Experimental evaluation of metal–organic framework desiccant wheel combined with heat pump

Reducing the consumption of high-grade energy on the regeneration side is crucial to decreasing the energy consumption of the desiccant wheel system. Metal-organic framework desiccants exhibit superior moisture absorption performance. However, there has been no research on the application of metal–organic framework materials in desiccant wheel systems for low-grade heat source regeneration. To address this research gap, this study applied a composite adsorbent of the metal–organic framework in a heat pump-desiccant wheel system and experimentally evaluated the performance of the heat pump-metal–organic framework desiccant wheel system using low-grade heat sources under different operating conditions. A comparison was made with electrically heated desiccant wheel systems and heat pump-desiccant wheel systems using traditional silica gel adsorbents. The results showed that the optimal desiccant wheel rotational speed was 8.63 r·h−1, and the optimal airflow was 300 m3·h−1. The energy consumption of the heat pump-metal–organic framework desiccant wheel system was only 42.77% of that of the electrically heated desiccant wheel system, and its dehumidification energy factor was 2.07, which is higher than that of the heat pump-silica gel desiccant wheel system. This demonstrates the feasibility and efficiency of utilizing low-grade heat sources for regeneration using metal–organic framework desiccants in practical applications.

Dry-column Vacuum Chromatographic Removal of Hg2+ from Wastewater Based on an Acridino-crown Ether-modified Spherical Silica Gel Adsorbent

Dry-column vacuum chromatographic technique is introduced for remediation of wastewater for the first time. A previously prepared chemically modified silica gel containing covalently immobilized Hg2+-selective acridino-crown ether selector molecules was used as an adsorbent. Removal of Hg2+ from highly contaminated river water was carried out to study practical applicability. Adsorption capacity, preconcentration factor, pH-sensitivity and selectivity in separation were determined. The adsorbent proved to be outstanding in selectivity, only Ag+ and Cu2+ interfered among 29 cations, was inert toward organic contaminants, exhibited regenerability and pH-independency between 3.0 ≤ pH ≤ 7.0. The proposed method showed a moderate efficiency in both adsorption (32 mg Hg2+ / 1 g adsorbent) and preconcentration (preconcentration factor of 100). A maximum 10 L of wastewater / 1 g adsorbent ratio is recommended as an upper limit for applicability. The described method showed a unique robustness and simplicity compared to conventional ion-chromatographic methods and an improved selectivity over physical interaction- or simple functional group-based adsorptions.

Study on ultrasonic depolymerization of Si-Ge precipitation in zinc oxide dust leaching process

Under the background of the increasing demand for germanium in high-tech, this paper finds out the mechanism of silicon germanium polymerization precipitation by simulating the leaching process of zinc oxide dust containing germanium. By comparing and analyzing the simulation experiments under ultrasonic and conventional conditions, the mechanism of efficient dispersion and depolymerization of germanium silicon precipitation induced by ultrasonic was found out. The results show that in the leaching process of germanium-containing zinc oxide dust, due to the increase of local pH, some silicon ions in the solution will hydrolyze and polymerize to form silicic acid colloid to adsorb germanium in the solution, causing the loss of germanium 14.81%, resulting in low recovery rate of germanium industry. Ultrasonic wave was introduced in the leaching process, and the shock wave and micro-jet released by ultrasonic cavitation continuously impacted the surface of polysilicate colloid. The germanium adsorbed on the surface of the silicic acid colloid is desorbed, and the large particles of silica gel are depolymerized into small particles of silicic acid, which reduces the adsorption of silica gel on germanium. The loss of germanium under ultrasonic conditions can be reduced by 59.35%. This study can effectively realize the efficient recovery of germanium in zinc oxide dust, and provide process and theoretical basis for the sustainable development of germanium industry.

Facile fabrication of silica aerogel supported amine adsorbent pellets for Low-concentration CO2 removal from confined spaces

Amine-based adsorbents show promise for removing low-concentration CO2 from environmental control and life support systems (ECLSSs), while the powder adsorbents are facing the challenges of reaction non-uniformity, pressure drop and material elutriation. To solve the problems, amine-based adsorbent pellets are fabricated by the extrusion–spheronization (ES), agar-assisted moulding (AM) and graphite-casting (GC) methods. The adsorbent pellets are further modified with pore-forming template for improved CO2 adsorption performance. The influences of granulation and pore-forming template modification on the structure-performance relationships of the adsorbent pellets are investigated. Granulation exerts adverse effect on the pore structure of tetraethylenepentamine supported on silica gel (TEPA-SG) adsorbent, which is not conducive to the bulk diffusion of CO2, and the CO2 adsorption capacity and kinetics thus have been impaired. The TEPA-SG-ES adsorbent pellets prepared by the extrusion–spheronization method show a relatively higher CO2 capture capacity of 1.01 mmol CO2/g due to better textural parameters and uniform dispersion of amine species. Thanks to the extrusion process, the adsorbent pellets also exhibit good mechanical properties with a high compressive strength of 10.90 MPa and low abrasion index of 0.36%. Both the textural properties and CO2 uptakes of the pellets can be restored upon template modification, and the promoting effect depends on the different templates employed due to their distinct pyrolysis rates and pathways. Mechanical properties will be adversely affected by the doped pore-forming template. The TEPA-SG-ES-UA pellets prepared with urea modification exhibit a great CO2 capture capacity of 1.48 mmol CO2/g and good mechanical properties with a high compressive strength of 4.90 MPa and a low abrasion index of 0.87%, and it could be a nice adsorbent candidate for removing low-concentration CO2 from ECLSSs.

Silica Gel Functionalized with Polyethylenimine as Advanced Sorbents for the Removal of Endotoxin from Gelatin

Gelatin is one of the essential materials for tissue engineering for its unique physicochemical properties. The endotoxin in gelatin needs to be controlled at a reasonable level to guarantee biosafety when applied to the human body. However, the isothermal titration calorimetry results showed specific interactions between gelatin and endotoxin, suggesting the difficulties of removing endotoxin from gelatin in mild conditions. In this work, a polyethyleneimine-grafted silica gel adsorbent for endotoxin was designed and prepared. Results showed that the prepared endotoxin adsorbent could remove endotoxin from gelatin without significantly changing the structures and properties of gelatin.

Experimental and computational study on utilising graphene oxide for adsorption cooling and water desalination

The adsorbent material’s thermal and sorption characteristics are the critical criteria that affect the adsorption systems’ overall performance. Therefore, this paper experimentally and computationally studies the utilisation of graphene oxide of a few atomic layers as a parent adsorbent material owing to its reported high thermal performance potential. Graphene oxide performance was benchmarked against the widely investigated silica gel adsorbent, emphasising adsorption cooling cum desalination application as the most needed to address the lack of sustainable cooling and clean water scarcity. Quantitative and qualitative analyses were undertaken to determine the influence of the evaporator temperature, cycle time and heat source temperature on the material and system levels. The results showed that graphene oxide enhances thermal performance by 44% compared to silica gel and adsorption by up to 57%. Furthermore, graphene oxide, compared to silica gel as a parent adsorbent, enhanced the system’s specific daily water production by up to 44.4%, the specific cooling power by up to 29.5%, the coefficient of performance by up to 17.2% and the exergy efficiency by up to 15.8%.

Adsorption of Fatty Acid Methyl Ester Derived from Squid Liver Lipid onto Silica Gel Adsorbent

The purpose of this study is the effective utilization of fisheries waste, squid liver, as a raw material of biodiesel. To obtain biodiesel from squid liver, extracted fatty acids are esterified with methyl alcohol. As the product of the esterification contains many by-products, the target product, fatty acid methyl ester of squid liver (SFAME), must be recovered from the products. SFAME is divided into three groups, which are saturated (SF), monounsaturated (MF), and polyunsaturated (PF) fatty acid methyl esters (FAMEs), based on the number of double bonds. In this study, the recovery of SFAME from the product of esterification through adsorption (i.e., dry washing) was investigated. Especially, the effect of solvents, toluene, and methyl alcohol on the recovery efficiency of SFAME using silica gel as an adsorbent was the focus. The competitive adsorption model successfully explained the present adsorption system, and the equilibrium adsorption constants and the saturated adsorption density could be determined by the model analysis. The equilibrium adsorption constant of PF was the largest among the SFAME (PF > MF > SF), and this order could correspond to the values of their dielectric constants. Methanol greatly affected the adsorption behavior of SFAME due to the fact of its hydrophilicity.

Evaluating the emerging adsorbents for performance improvement of adsorption desalination cum cooling system

The study aims to investigate the emerging adsorbents for adsorption desalination cum cooling system (ADCS) from the viewpoints of water production potential (WPP), specific cooling potential (SCP), energy required (ER), and coefficient of performance (COP). In this regard, five kinds of covalent triazine framework (CTF), five kinds of porous organic polymer (POP), and five kinds of ionogel based adsorbents are investigated as compared to five kinds of conventional silica-gel (SG) adsorbents. The well-known Dubinin-Astakhov (D-A) model, Clausius–Clapeyron equation, and ideal cycle governing equations were used to estimate adsorption equilibrium, isosteric heat of ad/desorption and the performance indicators, respectively. Among the studied adsorbents, A++, RD, Syloid 72FP + 57 wt% Emim-Ac, bipy-CTF500, and PS-II adsorbents produced relatively good results. However, nearly equivalent WPP (0.29 kg/kg/cycle) and SCP (710 kJ/kg/cycle) were estimated for A++, RD, bipy-CTF500 using ER of 2979, 2988 and 2992 kJ/kg/cycle, respectively. The PS-II adsorbent shows the WPR of 0.33 kg/kg/cycle and SCP of 790 kJ/kg/cycle using ER of 2983 kJ/kg/cycle. The performance estimated for Syloid 72FP + 57 wt% Emim-Ac found 5.6 folds higher as compared to A++ and could utilized as a potential adsorbent for ADCS. The COP of all the studied adsorbents estimated in range of 0.74 to 0.93.

Simple multi-residue analysis of persistent organic pollutants and molecular tracers in atmospheric samples

We present a simple, selective and sensitive analytical method to quantitatively determine a wide range of halogenated persistent organic pollutants and molecular tracers in atmospheric samples. Identification and quantification was carried out by high-resolution gas chromatography, hyphenated with low-resolution mass spectrometry operating in electron impact (EI) and electron capture negative ionization (ECNI) mode. Optimization on a number of instrumental parameters was conducted to obtain ultra-trace detection limits, in the range of few fg/m3 for organohalogen compounds. Repeatability and reproducibility of the method was thoroughly evaluated. The analysis was validated with standard reference materials and successfully applied to actual atmospheric samples. The proposed multi-residue method provides a precise, affordable and practical procedure of sample analysis for environmental research laboratories with conventional instrumentation on a routine basis.•A simple combination of alumina, florisil and silica gel adsorbents was applied to sufficiently isolate polychlorinated biphenyls, organochlorine pesticides, polycyclic aromatic hydrocarbons, long chain n-alkanes, hopanes and steranes.•Full elution was achieved in two successive fractions, using small volumes of n-hexane and n-hexane/dichloromethane to recover all target substances.•To maximize analytical response, optimization was applied for three operating parameters in ECNI mode: i) ion source temperature; ii) emission current; and iii) electron energy.

Adsorption removal of styrene on C–Cl grafted silica gel adsorbents

The heat desorption of styrene from adsorbents is impracticable owing to its spontaneous polymerization under heating conditions. However, the feature also brings a potential promoting effect on styrene adsorption. Therefore, it is expected to develop the non-regenerative adsorbents with large adsorption capacity by strengthening the polymerization effect. In this work, C–Cl grafted silica gel adsorbents were prepared by introducing (Chloromethyl)dimethylchlorosilane (CMDMCS) and FeCl2 into silica gel. The C–Cl grafted silica gel exhibited excellent styrene adsorption performance, its adsorption amounts for styrene were 4.67 times and 9 times of unmodified silica gel under dry air condition and high humidity condition (RH = 80%), respectively. In addition, the adsorption of styrene on C–Cl grafted silica gel was almost unaffected by the presence of toluene. The characterization of adsorbents after styrene adsorption indicated that the improvement of adsorption capacity of C–Cl grafted silica gel for styrene can be attributed to atom transfer radical polymerization (ATRP) of styrene molecules on modified silica gel during adsorption process.

The application of silica gel synthesized from chemical bottle waste for zinc (II) adsorption using Response Surface Methodology (RSM)

The application of silica gel adsorbent synthesized from chemical bottle waste to remove zinc ions in the solution has been carried out. The synthesis of silica gel was carried out using alkaline fusion followed by sol-gel reactions. The chemical glass bottle container was made from borosilicate glass which was different from glass bottles for food and beverage that has been studied in previous studies. The Zn2+ adsorption was optimized using Box-Behnken Design (BBD). Box-Behnken Design was applied to study the optimum zinc ion removal and the input variables interaction. The input variables optimized were adsorbent dosage (1.0 – 2.0 g), initial zinc ion concentration in the solution (25 – 100 ppm), contact time (15 – 45 min), and pH (4 – 9). Response Surface Methodology (RSM) was applied to visualize the input variables' correlation to zinc ion removal. The optimum zinc ion removal was achieved at an adsorbent dosage of 2 g, initial concentration of 35 ppm, contact time of 45 min, and pH 8, which was 99.56%. The optimization of adsorption isotherm obtained that the adsorption follows the Langmuir isotherm model. The silica gel obtained was characterized using SEM-EDX and BET to obtain silica gel properties. The SEM-EDX showed a spherical shape of silica gel. Silica gel containing zinc (Zn) was observed from SEM-EDX after the adsorption process. A pore diameter of 42.098 nm and surface area of 297.083 m2/g were obtained from BET analysis of synthesized silica gel.

Theoretical and Experimental Adsorption of Silica Gel and Activated Carbon onto Chlorinated Organic Compounds in Water: A Case Study on the Remediation Assessment of a Contaminated Groundwater Site

Chlorinated organic compounds (COCs) are a serious threat to human health and the ecological environment due to their toxicity, mutagenicity and carcinogenicity. A number of corresponding treatment techniques have been developed thus far; among these techniques, adsorption is considered an efficient and low-cost method. However, it is very important to find suitable and economical adsorbent types and usage amounts. In this study, the adsorption of trichloroethylene (TCE) and perchloroethylene (PCE) onto two different adsorbents (silica gel and activated carbon) was investigated, and the obtained adsorption constants were then introduced into Langmuir and Freundlich adsorption models. The adsorption isotherm constants of these two models were used to predict the adsorbate removal efficiency and the required adsorbent mass. The results showed that the Langmuir and Freundlich models predicted the removal efficiency and adsorbent quality of the TCE and PCE adsorbed onto silica gel and activated carbon, and the errors were less than 10% compared with the measured values obtained through adsorption experiments. According to the differences in adsorption efficiency and cost between silica gel and activated carbon, it was found that, when the adsorption efficiency of the silica gel for TCE and PCE significantly decreased, adding activated carbon to continue the adsorption effectively reduced the adsorption cost of on-site remediation. This result was demonstrated by taking the Radio Corporation of America (RCA) pollution incident in Taiwan as an example, and it was estimated that 6427 ± 172 tons and 343 ± 21 tons of silica gel and activated carbon, respectively, would be required for the on-site remediation of TCE, and the total cost would be approximately 4,390,000 USD. The remediation of PCE would require 7553 ± 57 tons of silica gel and 350 ± 68 tons of activated carbon, with a total cost of approximately 5,030,000 USD. Therefore, silica gel should be used to reduce the pollutant concentration first, and then activated carbon should be added for continuing adsorption. This method of adding adsorbents is economical and can effectively reduce the adsorption cost.

Pemurnian Bioetanol Menggunakan Adsorben Silika Gel dari Limbah Botol Kaca di Industri Kecap

Waste glass bottles is an inorganic waste that amounts to 0.7 million tons per year with the main content of silica, so it can be used as the main ingredient to produce silica gel. In the soy sauce industry, waste glass bottles came from depalletizer activities, the activity of moving glass bottles to the cleaning area. This research aims to utilize waste glass bottles as a raw material for producing silica gel adsorbents using the hydrothermal method and the sol-gel approach. Silica gel becomes an adsorbent in the purification of bioethanol from wastewater washing dissolving tanks using the adsorption method. Variations in the bioethanol production are yeast weight as 0, 2, 5, and 8 g as well as fermentation time for 4, 7, and 10 days.The bioethanol purification process used variations in adsorption time for 40, 60, and 80 minutes. Characterization of silica gel using BET and SEM-EDX test. The BET test results show that activated silica gel has a surface area of ​​231,851 m2/g. Analysis by SEM-EDX showed that the Si and O elements in activated silica gel were 40,94% and 51,92%. Based on the results of the GC-MS test, 60 minutes is the best adsorption time to increase the bioethanol content from 39,8±9,9% to 72,0±1,1%.